In recent years, reduction in pixel size has been proceeding in a solid-state imaging unit such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. Accordingly, the number of photons entering a unit pixel decreases. Therefore, sensitivity is decreased, and S/N ratio is decreased. Further, when a color filter configured of primary-color filters of red, green, and blue that are arranged two-dimensionally is used for colorization, green and blue lights are absorbed by the color filter in a red pixel. This results in decrease in sensitivity. Moreover, an interpolation process is performed between the pixels when generating each color signal. This results in occurrence of so-called false color.
Therefore, there is proposed a solid-state imaging unit in which three photoelectric conversion layers are laminated in one pixel, and photoelectric conversion of red light, green light, and blue light is performed in the respective photoelectric conversion layers to obtain signals of three colors in one pixel (for example, Patent Literature 1). In Patent Literature 1, for example, an organic photoelectric conversion section that detects green light and generates a signal electric charge in correspondence therewith is provided on a silicon substrate. Also, photodiodes (inorganic photoelectric conversion sections) that detect respective red and blue light are provided in the silicon substrate.
Also, Patent Literature 2 proposes a structure that achieves a laminated structure of the organic photoelectric conversion section and the inorganic photoelectric conversion section as described above in a so-called back-illumination-type solid-state imaging unit. In the back-illumination-type solid-state imaging unit, a circuit and a multi-layered structure of wirings (hereinafter, simply referred to as “wiring layer”) are formed on a surface of the silicon substrate opposite from a light receiving surface. Therefore, the organic photoelectric conversion section is allowed to be provided on the silicon substrate (the inorganic photoelectric conversion section) with no wiring layer in between. Therefore, in a pixel, a distance between the organic photoelectric conversion section and the inorganic photoelectric conversion section is allowed to be shorter. Therefore, it is possible to reduce variations in sensitivity between colors resulting depending on an F-number of an on-chip lens.